Joint reception, or coordinated multipoint reception (CoMP), of uplink transmissions from user equipment units is a method for enhancing the reception quality of transmissions received from user equipment units. When performing a joint reception of uplink transmissions, a serving node receives user data from a user equipment unit, both directly from the user equipment unit and from another network node, a so called cooperating node, which cooperating node receives the uplink transmissions and forwards user data to the serving node.
D1 (US2011/0080879) describes coordinated multipoint (CoMP) reception of uplink signals in a cellular radio communication system (see §2). Uplink signals are received at multiple antennas by a plurality of adjacent radio access points (§4). The received uplink transmissions are subjected to a joint reception (§5). To reduce complexity during the joint processing, the system of D1 does not use all possible antennas for the reception. Instead only a subset of antennas are used (§6). Typically, the antennas where the strongest signal strengths can be expected are selected. D1 suggests measuring the downlink signals received by the user equipment in question (see claim 1 of D1).
Joint reception, as in D1 or otherwise, is beneficial in providing an enhanced reception of the uplink transmissions than single-node reception. However, joint reception requires that a cooperating node transfer user data to the serving node. Such transfer in a transport network is typically referred to as backhaul transmissions.
Since joint reception is beneficial compared to single-node reception a need to use joint reception arises. However, using the backhaul for joint reception may not always be possible since there is a risk of congestion in the backhaul links. If the backhaul is congested, the joint reception may fail or be delayed. Such congestion may not be avoided even if the number of reception points is limited, as in D1.